Temporal and habitat adaptations in Drosophila subobscura populations: changes in chromosomal inversions

In insects, chromosomal inversion polymorphism has been related with different adaptations, including global warming. Regarding this environmental change, Drosophila subobscura stands out as a useful model species due to its rich inversion polymorphism covering the whole karyotype. The main aims of this research were to analyze the differentiation of this polymorphism in Jastrebac Mt. (Serbia) depending on the different habitats (beech and oak forests) and over time. These latter changes were studied in relation to climatic variables (mean, minimum and maximum temperatures, humidity and rainfall). Microdifferentiation was observed between beech and oak forests, mainly for the A and O chromosomes. However, the changes over time turned out to be larger than those due to habitat. In Jastrebac Mt., temperatures increased over time, with this increase being significant for mean and minimum one. The Multidimensional Scaling analysis showed a relation between chromosomal inversions and temperatures (mainly minimum) in Jastrebac Mt. and other Serbian populations of D. subobscura. In beech forest of Jastrebac Mt., the Chromosomal Thermal Index increased over time from 1990 to 1994, but showing a possible stabilization in 2023. This result was observed in other studied Serbian populations. Although those are preliminary results, it might hypothesize that there may be a threshold for the action of natural selection, increasing 'warm' adaptive inversions and decreasing 'cold' ones. The possible reasons for this hypothesis are also discussed.